My truck continues to die like it has run out of gas after about 4-5 miles of City driving, and then will restart in about 10 minutes. I can go much further with highway driving. It starts fine every morning.

I have a 1974 F-100 4 x 4 (pic attached), with a 1978 - 400M engine, and have owned for two years and never stop upgrading. Previous owner had no information on the truck at all.

I have replaced fuel pump, installed a new stock 2bbl Motorcraft carb, fuel filter, plug wires, insulated fuel line from radiator hose, new PCV, new coil and plugs, and the cooling system is fine. I believe all vacuum hoses are correct and working fine. I am completed stumped, and greatly appreciate any suggestions.

On another note, gas gauge does not work and fuse is fine. Could this possibly be the sending unit and float in tank itself? Again, any info would be helpful.

thx,
Eric in AZ

 

Sounds most likely a fuel problem.

How clean is the tank itself? And have you replaced all rubber fuel lines from tank to carb?

Crud in the tank can plug the filter sock. Old fuel lines affected by time and alcohol can get soft and sucked shut. Heat from around town driving can aggravate the problem of fuel starvation (eg vapor lock).

 

Nice looking rig. Keep at it... you'll get there.

If it dies, I'd look at the fuel and ignition system.

Fuel.. drain the tank and inspect what comes out... silty? sediment? Is the tank corroded? How do the lines look?

Is the fuel float sunk or bobbing around loose in the tank??

Ignition... electronics don't work well when old or hot. Ya might want to refresh the system (ICM, pickup, Pertronix?) and keep the parts ya remove as temporary spares.

.

 

Thanks for messages on fuel tank and lines, and there is a good chance these are the culprit. I would imagine the inside of tank is in rough shape. I have thought about upgrading to LMC's much larger tank and sending unit + replacing lines.

I will also replace some additional fuel lines, and explore upgraded ignition.

Thanks again.

 

Welcome to FTE btw

The "after ten minutes" part sounds like ignition. Except one would figure that it would occur when highway driving too, not just city driving or stop and go. Have you checked for spark right when this happens? Carry a spare plug and pull a wire, ground it, and crank the starter. Check for a good fat, whitish-blue spark. Thin red or yellow is no good.

 

If it dies when hot and won't restart until cool, that would be characteristic of a hall effect that is failing. If so, you may need a new distributor pickup coil.

They are inexpensive and are heat sensitive, increasingly so with age.

Get the truck warmed up until it stalls, then quickly check for spark.

 

Do you recall the LAST work you did to your truck before this happened? Sometimes that is the logical starting point.

My dad replaced the ignition module on a 77 F150 we had in the 1990s, but he never told me that he had to cut the wires and splice them back together. It would run fine and then immediately die. And after a few minutes it would start again.

Only after many times being stranded and hounding him to what exactly he had done recently did he mention cutting and splicing the wires. Needless to say, he got the wires crossed.

If you can get a buddy with you next time it fails pull the distributor wire and hold it to something on the engine and see if you get an electrical spark across the gap. If not, it is electrical, if yes, fuel related.

 

First thing I would check is your gas cap. It may not be venting properly, and only allowing the air to creep back in after sitting 10 minutes or so. When it shuts off, open the gas cap and if the tank sucks in air, get a new vented cap.

 

Nice looking dentIf you do decide to go with a new gas tank, explore other options besides LMC. They charge a fortune for shipping! Try looking at the outfits that offer free shipping for purchases over $100. I bought my gas tank at AutoZone. The advantage to that was inspecting the unit right there for any dents, etc! If your tank and fuel lines are clean, I would lean towards the ignition module. Keep at it. Once it purrs like a kitten, it will be all worth it.